Today, the polyethyleneterephthalate (PET) with high tenacity decreases the deformation of the composite structure it forms with the rubber significantly with its high strength and low elongation properties, thus material with higher performance can be produced. The PET fiber is most commonly used in tire, hose, components such as conveyor band and belt as rubber reinforcement material.
The synthetic fibers are hard to adhere to rubber without binding agents in between them because they have a very smooth surface and low reactivity. The low surface activity of the fibers stems from the low polarity and low reactivity of the polymer molecules. Therefore, adhesives are used in intermediate surfaces since the physical and chemical bonding between the rubber and cord fabric used in the tire production technology is very low. Adhesives vary according to the type of the polymer used in cord fabric.
Since the elongation of cord fabric material is low and its strength is high, and the elongation of the rubber material is high and its strength is low; the adhesive which is used should provide an excellent intermediate surface in order to provide the best performance. Increasing adhesiveness provides better compatibility between the rubber and the cord fabric, and enables the properties of both rubber and cord fabric to be revealed better in the final product.
As it is in reinforcing materials such as nylon, rayon, aramide; an adhesive should be applied in order that the PET cords are adhered to the rubber. In cord fabric production, water based Resorcinol-Formaldehyde-Latex (RFL) adhesive solutions enabling the cord fabric to rubber have been used for over fifty years. In RFL adhesive solutions, caustic and ammoniac are the most commonly used catalysts. In the said solutions, different Formaldehyde/Resorcinol (F/R) mol ratios, resin/latex ratios, solid ratios and additional activating chemicals are used for especially PET fiber.
Whereas the adhesion of fibers such as nylon and rayon are easy to adhere to the rubber with RFL, there are difficulties in adhesion of PET fiber to the rubber. The main reason for this is that functional groups such as carboxyl (COOH) and hydroxyl (OH) forming bonds with the RFL are only present on chain ends of PET molecule in structure of PET fiber. In nylon and rayon material, the density of the functional groups is much higher than in the PET fiber. For this reason, the adhesive systems of PET fibers are continuously developed. One of the said methods is to develop spinfinish materials that will increase the surface activity of PET fiber with RFL applied during yarn production.
Spinfinish materials are mostly liquid compositions which are comprised of more than one components and wherein all components are in equilibrium. Applying spinfinish material which is a very important part of fiber production procedure provides various properties to the fibers, as well as provides ease by forming intermediate surface between the fiber surface and the metal and/or ceramic components present in the production procedure.
The main functions of the spinfinish material are to provide lubrication by greasing the fiber surface, to prevent abrasions by minimizing the friction between filament-filament, filament-metal and filament-ceramic, to provide antistatic properties to the fiber, and to prevent the fiber from falling apart by keeping the hundreds of filaments forming the fiber. During the production of synthetic fibers used as rubber reinforcing material and produced in high speeds, spinfinish is applied on the fibers coming out of spinnerets in order to drawability of the fiber. It is not possible to produce fiber with high performance in high speeds without spinfinish. The said spinfinish material is used for providing drawability in nylon 6.6 fibers, whereas it is also used to activate the surface of the fiber besides the said property in PET fiber production.
The spinfinish which has a very important role in production of fibers with high performance causes many problems in spinning, drawing and twisting processes when they are not compatible with the system it is used with. These can be breakage in fiber, filamentation, winding in drawing cylinders and irregularity in reel form, being smoked, tar forming which cannot be cleaned, unevenness in the reel form, deteriorations in twisting quality and ruptures. For this reason, the spinfinish material used for producing fiber with high quality should have some main properties.
High decomposition temperature, high smoking temperature, optimum viscosity, antistaticity, not leaving residue on the metal/ceramic components, low volatility are among the expected major properties. Besides, the spinfinish which is used being harmless to the environment and human's health, providing emulsion quality in aqueous solution, being resistant to the temperature in process conditions, not experiencing chemical reactions, not being oxidized in storage conditions and being low cost also provide advantage in production of fibers.
U.S. Pat. No. 4,348,517, an application known in the state of the art, discloses a spinfinish composition applied in two stages on PET fiber. The said composition is stated to be comprised of triglycidyl glycol ether and epoxy silane.
U.S. Pat. No. 3,803,035, another application known in the state of the art, discloses a spinfinish composition comprised of lubricant, antistatic agent, emulsifier and polyepoxy.
U.S. Pat. No. 3,793,425, another application known in the state of the art, discloses coating PET fiber with a solution comprised of epoxy resin buffered with potassium carbonate sodium carbonate or ammonium hydroxide.
U.S. Pat. No. 4,054,634, another application known in the state of the art, discloses a two stage spinfinish application. Spinfinish applied in first stage comprises polyethyleneoxide-polypropyleneoxide (EO-PO) monoethers, whereas in spinfinish composition applied in second stage compositions comprising catalysts such as epoxy silane and sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, sodium acetate, potassium acetate are disclosed.
The compositions disclosed in the said methods are high cost and/or harmful to environment. Most part of them cannot provide the desired adhesion between the fiber and rubber and the strength. Furthermore, there is no study for applying spinfinish on fiber in single stage during the production of fiber.